The work described in this grant proposal continues our investigation of the effects of immunizing pregnant women with tetanus toxoid on the level and duration of immunity to tetanus in their offspring and the response of the offspring to postnatal immunization with tetanus toxoid (as a component of DPT). The primary setting for the study is the Obstretrics Clinic of Magee-Womens Hospital where there is a carefully selected and immunologically defined patient population. Both the mothers and their offspring are being tested for immunity to tetanus by lymphocyte transformation and by a sensitive radioimmunoassay for IgM ad IgG antibody to tetanus which was developed as part of this study. A subsidiary study is being done in a collaborative fashion with the Departments of Hygiene and Obstretrics at the University of Athens where a large clinic population is being immunized and tested for serum antibody. Ths study will provide basic knowledge about the transplacental sensitization of the human fetus and will lead to the development of prenatal vaccination procedures that will povide the newborn with protection against infectious agents. Such protection is especially useful in the medical care of the poor in our country, particularly in those areas where perinatal care is sporadic and often not delivered by a physician, and in underdeveloped coutries where the problems of medical care are even more acute.